Gilbert Newton Lewis

We frequently define an acid or a base as a substance whose aqueous solution gives, respectively, a higher concentration of hydrogen ion or of hydroxide ion than that furnished by pure water. This is a very one sided definition.

We may say that a basic substance is one which has a lone pair of electrons which may be used to complete the stable group of another atom, and that an acid is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms.

It must be admitted that science has its castes. The man whose chief apparatus is the differential equation looks down upon one who uses a galvanometer, and he in turn upon those who putter about with sticky and smelly things in test tubes.

If a man made himself an expert in any particular branch of human activity, there would result the strong tendency that a peculiar aptitude towards the same branch would be found among some of his descendants.